So they really have no

In reply to The Penguin Grid:

So they really have no practical use for a person using this grid to lay out typography?

The grid was put to use designing some of the most iconic paperback covers of the twentieth century.

Perhaps these will help:

http://thebookdesignblog.com/book-design-articles/history-marber-grid

http://www.eyemagazine.com/feature/article/penguin-crime-text-in-full